SUMMARY (See instructions); Invasive infections due to non-typhoidal salmonella strains (NTS) appear to be emerging as a common cause of bloodstream infection in sub-Saharan Africa. As many as 40% of blood culture isolates from bacteremic children and 20% of blood culture isolates in children with severe pneumonia are due to NTS in Africa. While the exact reasons for the high burden and severity of disease due to invasive NTS are incompletely understood, it appears that transmission of NTS may be largely due to human-human contact in Africa. This is in contrast to the largely foodborne route of transmission seen in other areas of the world Differences in host characteristics (high rates of HIV, malnutrition) and differing socio-economic conditions (poor access to clean water and sanitation, more rural environment) may contribute to human-human risk of transmission. In addition, it is possible that pathogen specific differences may also be important in increasing the diversity and virulence of NTS isolates in Africa. We propose to more clearly define the epidemiology of NTS disease in Africa by examining differences in host susceptibility, changes in strain diversity and virulence, and the role of asymptomafic carriage in promofing human-human transmission of NTS.